Characteristics And Physical Causes Of Interannual And Interdecadal Variability Of Sea Ice In The East Siberian-Beaufort Sea In Autum

Arctic sea ice is a key element of the Earth’s climate system,playing a crucial role in the local ecological environment and the atmospheric circulation in the middle and high latitudes.As one of the main sources of cold air in Eurasian winter,the sea ice over the Barents-Kara Sea has received much attention in previous studies.As climate change continues to intensify,the activity and climate impacts of sea ice in other regions of the Arctic are becoming increasingly evident.For example,recent studies have highlighted the important impact of the autumn East Siberian-Beaufort(Es CB)sea ice on the following winter and spring climate in Eurasia and North America.However,the current academic has poorly understood the Es CB sea ice variability and related physical processes,which is not conducive to operational short-term climate prediction.In this study,the characteristics and physical sources of autumn Es CB sea ice variability on interannual and interdecadal scales are investigated by using the reanalysis data and coupling model simulation data.The main conclusions are as follows:(1)In the autumn of the Northern Hemisphere(August-October),the Es CB sea ice reaches the climatological minimum,and it is the most intense part of seasonal melting of simultaneous Arctic sea ice,showing obvious interannual variability with significant spectral peaks mainly concentrated in 2-3 and 4-6 years.Furthermore,the interannual variability of autumn Es CB sea ice is mainly related to the North Atlantic Oscillation(NAO)pattern atmospheric circulation anomalies in the preceding summer(May-July),rather than the direct effect of the contemporaneous atmospheric circulation.In the negative NAO-like phase,the entire layer of the Arctic is controlled by anomalous high pressure.Anomalous warming caused by the enhanced adiabatic subsidence over Greenland and the low-level anticyclonic circumpolar circulation generate the warm advection anomalies,which are conducive to the contemporaneous melting of the Es CB sea ice.The associated Es CB sea ice anomalies can be maintained or even intensified by the local sea ice-albedo positive feedback until autumn.Therefore,the abnormal signals of Arctic sea ice tend to show significant persistence in summer and autumn.In addition,the generated observed physical processes can also be verified in the historical simulation of the E3SM-1-0 model,which further increases the reliability of the results.This physical process of the preceding atmospheric circulation affecting the subsequent sea ice provides a scientific basis for the seasonal prediction of the Es CB sea ice and the assessment of related climatic impacts.(2)Apart from the interannual variability,the autumn Es CB sea ice also exhibits significant interdecadal variability.As the core region of interdecadal variability of autumn Arctic sea ice,its corresponding interdecadal component accounts for more than 40% of the total variance of sea ice concentration anomalies.Our further analyses show that the autumn Es CB sea ice is mainly associated with the Atlantic Multidecadal Oscillation(AMO),while the connection with the Interdecadal Pacific Oscillation(IPO)is weaker.In the positive AMO phase,North Atlantic warm SST anomalies excite poleward propagating atmospheric Rossby waves,favoring the establishment of an anomalous high over the central Arctic region.The corresponding adiabatic subsidence is strongest in the Es CB region,resulting the warming in the lower troposphere,which causes the Es CB sea ice to melt.Meanwhile,surface warming and Es CB sea ice melting can simultaneously give rise to an increase in local cloud amount and downward longwave radiation,further enhancing the surface air temperature.This surface air temperature-cloud-longwave positive feedback is beneficial for the long-term maintenance of the decadal sea ice signals.In addition,the Atlantic pacemaker experiments of the Had GEM3-GC31-MM model can realistically reproduce the observed physical process as shown above,further supporting the conclusions of the observation.These results have important scientific references for understanding and predicting the interdecadal changes in the Arctic sea ice.